Twitter works pretty well too, especially if the people you follow end up focusing more on politics than whatever you actually followed them for.

So true

I've encountered this view of Facebook discourse quite a few times on HN and I continue to be confused and perturbed by it so I must speak up.

I value HN because among the many things the OP mentioned, it very often gives me vastly different and contrasting views on topics. Facebook does not do this. However, with that one exception (i.e. it's filterbubblish) I've generally found Facebook comments to be of extremely high quality. Is it just the company I keep or am I not the only one?

It's your "private FB" vs "public FB" -- i.e. comments on news articles, big viral shares, etc.

Facebook and Reddit are both great places to have a mature discussion on tech. But which groups you join matter a lot.

Neither highlights new things as well as HN, but I feel median comment quality is better there.